Conventional examples of the application field of waveguides include (1) a communication device and (2) a radar device.
If assuming that there is a plurality of the above-described communication devices and there is a limitation on the size of their installation locations, there may arise necessity of connecting between waveguides of a certain communication device and another one. Those waveguides have different propagation directions of electromagnetic waves (hereinafter referred to as “a tube axis direction”) which are propagated in the respective waveguides, and also have different direction of polarized waves (hereinafter referred to as “a polarization direction”).
As a conventional waveguide device for changing the tube axis direction, there has been generally known a device called a waveguide bend or a waveguide corner, which has a structure formed by bending the waveguide (e.g., Patent Literature 1 below).
Patent Literature 1 discloses a structure, in which two waveguides are connected at a desired angle. Each of the two waveguides has a waveguide whose propagation path (hereinafter referred to as “a waveguide path”) of electromagnetic waves is formed in a rectangular cross-sectional shape (hereinafter referred to as “a rectangular waveguide”). In addition, each waveguide is formed to include a step-like step face at a bend part where the tube axis direction is changed.
Note that, in the following description, the term “waveguide path” is used for indicating not only the propagation path itself, but also a structure defining the propagation path, such as an internal wall, or the both cases.
With regard to the rectangular waveguides, when considering a TE10 mode as a propagation mode used in many cases, a wide plane of an internal wall defining the waveguide path is sometimes called an “H-plane”. This is because the wide plane is parallel to a direction of a magnetic field (H). On the other hand, a narrow plane of the internal wall is sometimes called an “E-plane” because the narrow plane is parallel to a direction of an electrical field (E).
The waveguide bend as described in Patent Literature 1 is sometimes called an E-plane bend (or corner) or an H-plane bend (or corner) depending on a plane along which the tube axis direction is changed. The waveguide bend of the above-described Patent Literature 1 corresponds to the E-plane bend.
In the case of the waveguide bend described in Patent Literature 1, the respective tube axis directions in two straight tube-shaped waveguide parts provided on the both sides of the bend part correspond to the central axes of the respective waveguide parts. In addition, straight lines indicating the tube axis directions in the two waveguides parts are in a relationship of being positioned on the same flat plane, and of intersecting each other at one point. Furthermore, long side directions of the cross-sectional shapes (rectangle in the case of Patent Literature 1) of the waveguide paths of the respective waveguide parts are parallel to each other.
Meanwhile, there has been known a waveguide device which changes the polarization direction without changing the tube axis direction (e.g., Patent Literature 2).
The waveguide device described in Patent Literature 2 discloses a polarized wave converter having a slit with a specific cross-sectional shape, which is disposed between two rectangular waveguides (i.e., a vertically-polarized wave waveguide and a horizontally-polarized wave waveguide) whose polarization directions are orthogonal to each other.
Patent Literature 1: JP 9-246801 A
Patent Literature 2: JP 3884725 B1